How to preview Markdown in Chrome without an extension that reads your data
You shouldn't need to grant an extension access to everything you browse just to render a Markdown file. Here's a local Markdown preview that doesn't ask for that.
The permissions problem with Markdown extensions
If you search the Chrome Web Store for "Markdown preview," most results are extensions that request the same alarming permission: "Read and change all your data on websites you visit."
The permission is technically required for the approach these extensions use — injecting a content script into pages so they can intercept .md file requests or add a preview panel to GitHub. But from a user perspective, granting that permission means the extension can read everything you do in the browser: your email, your banking portal, your internal tools, your browsing history.
For a Markdown preview utility, that's a disproportionate trade-off.
The alternative is a different architecture: a side panel or popup that accepts input directly, renders it locally, and doesn't interact with pages at all. No host permissions needed because nothing is being injected anywhere.
The system
Step 1: Open the Markdown tool in Toolbelt
Install Toolbelt and open it from the Chrome toolbar. Select the Markdown Preview tool from the side panel.
Toolbelt has no host permissions — it doesn't read your tabs or interact with any pages. The Markdown tool accepts input directly in the panel.
Step 2: Paste or type your Markdown
Paste the Markdown you want to preview into the input area. The rendered preview appears alongside it in real time. This works for:
- README content you're writing before pushing to a repository
- Notes in Markdown format that you want to check before sharing
- Documentation snippets you're editing
- Any Markdown pasted from an editor, email, or another source
Step 3: Iterate on the content
The preview updates as you type or edit. Make changes in the input, see the result immediately. When the preview looks right, copy the raw Markdown from the input area (or the rendered HTML from the preview if you need it) and paste it wherever it's going.
When to use a different approach
The side panel tool is the right choice when you're writing or reviewing Markdown that exists as text in a document or clipboard — working notes, documentation snippets, README drafts.
For a workflow where you frequently need to preview .md files directly from URLs (fetched from a server, opened from disk), a dedicated extension with appropriate permissions, or a desktop editor with built-in preview (VS Code, Typora, Obsidian), is more ergonomic. The trade-off is the permissions scope.
For GitHub specifically, the native rendered view on github.com is the simplest answer — no extension required.
Common mistakes
Installing a broad-permission extension for occasional Markdown use. If you preview Markdown a few times a week, a side panel tool is adequate and requires no sensitive permissions. Broad-permission extensions are appropriate only if you're doing constant Markdown review of files served from URLs.
Expecting support for non-standard Markdown dialects. If your Markdown uses custom extensions (Hugo shortcodes, Docusaurus syntax, MDX components), a generic renderer won't process them correctly — you'll need a preview environment specific to your publishing tool.
Related reading
- Free image tools that work without uploading your files
- Chrome extensions that don't read your page content
- Toolbelt — client-side dev and design utilities for Chrome
FAQ
Why do Markdown extensions need such broad permissions?
Most Markdown preview extensions work by injecting a content script into pages — this is how they intercept .md files served from a URL, or add a preview pane to GitHub. To do that, they need the "read and change all your data on websites you visit" permission. That's technically necessary for the approach, but it means the extension has access to everything you do in the browser, not just Markdown files.
What's the alternative to a content-script approach?
A side panel or popup that accepts pasted or typed Markdown input and renders it locally. You lose the ability to automatically preview .md files you open in a tab, but you gain a privacy guarantee — the extension never reads your tabs or browser activity.
Can I preview GitHub README files without a broad-permission extension?
GitHub renders Markdown natively in the browser, so you can read rendered README files directly on github.com without any extension. The side panel tool is more useful for Markdown you're writing yourself — notes, docs, messages — that you want to check before posting or publishing.
Does Toolbelt support all Markdown features?
It supports CommonMark-spec Markdown — standard headings, bold, italic, links, images, lists, blockquotes, code blocks (with syntax highlighting), and tables. GitHub Flavored Markdown extensions (task lists, strikethrough) are also supported. More exotic features like footnotes or custom directives may not render.